1. Field of the Invention
The present invention relates to an active matrix type display device. More specifically, the present invention relates to a display device having a drive circuit (driver) along one side of an active matrix substrate.
2. Description of the Related Art
An active matrix substrate, which is prepared by forming scanning lines and signal lines in a matrix configuration on a substrate and forming a driving element such as a TFT (Thin Film Transistor) at the intersections of these signal lines, has been used generally for a liquid crystal display device and the like. In such a conventional active matrix substrate as shown in FIG. 17, a scanning line drive circuit 91 is provided at one end of the scanning lines G arranged in parallel or substantially parallel to each other, and a signal line drive circuit 92 is provided at one end of the signal lines S arranged in parallel to each other and perpendicularly to the scanning lines G. Namely, in a conventional active matrix substrate 90 as shown in FIG. 17, the scanning line drive circuit 91 and the signal line drive circuit 92 are provided respectively on the adjacent two sides in a peripheral region 94 of a pixel region 93.
According to the recent development in the semiconductor manufacturing technology, the trend for higher integration of a drive circuit has been advanced. For a display device, it is desired to downsize the cabinet of the display device while maintaining the size of the display region, and thus an important object for resolving this problem is to narrow the frame. Due to the circumstances, an attempt to mount both a scanning line drive circuit and a signal line drive circuit on only one side of a peripheral region of an active matrix substrate has been carried out (see, for example, JP 2003-241217 A).
Specifically, as shown in FIG. 18, JP 2003-241217 A (see FIG. 4 of this document) discloses a constitution where a drive circuit 98 formed by integrating a scanning line drive circuit and a signal line drive circuit is mounted on only one side of an active matrix substrate 95.
This document discloses also in FIG. 3 and the like a constitution where a scanning line drive circuit is arranged on one side of the active matrix substrate 95 and where signal line drive circuits are arranged on both sides of this scanning line drive circuit. In the conventional active matrix substrate as shown in FIG. 18, the plural signal lines S disposed in parallel to each other are led out respectively to the both sides of the pixel region 96 alternately and connected to the drive circuit 98, thereby equalizing the widths of the frame region 97 in the extending direction at the both sides of the signal lines S.
The conventional constitution as shown in FIG. 18 has been employed preferably to display devices especially for smaller electronic equipment such as portable telephones, digital cameras, and PDAs (Personal Digital Assistants).
However, due to the recent trend for higher resolution of display devices, the numbers of signal lines wired on a frame region have increased rapidly. Particularly, in a high-definition panel with numbers of signal lines, it is required to reduce the width of each signal line and the intervals between the signal lines, and degradation in the yield caused by wiring leaks and breaking of wire cannot be avoided. Therefore, in such a high-definition panel, when an improvement in the yield is required, the frame width cannot be decreased due to the restriction in the wiring layout of the active matrix substrate.
A counter substrate that faces the active matrix substrate has a common electrode formed on the whole surface. To this common electrode, a predetermined voltage (common voltage Vcom) is applied via a common wiring 101 from a drive circuit (not shown in FIG. 18) provided for example on an active matrix substrate or a FPC (Flexible Printed Circuit) connected to the active matrix substrate. In such a case, a contact 102 (referred to as “common transfer”) for electrically connecting the common wiring 101 and the common electrode on the counter substrate is provided on the active matrix substrate 95. The common transfer 102 is formed of an electroconductive material such as carbon paste and gold, and it has a cross sectional area of about 500 μm2 to 1 mm2. When a drive circuit 98 is arranged on one side of the peripheral region of the pixel region 96 as shown in FIG. 18, the common transfer cannot be arranged around the drive circuit 98 since lead wirings from the drive circuit 98 are crowded there. Therefore, as shown in FIG. 18, the common transfer 102 is arranged on a region of the frame region 97 of the active matrix substrate 95 where the lead wirings are not provided. It is also required to lead the common wiring 101 along the periphery of the pixel region 96 from the drive circuit side to the common transfer 102.
The common wiring 101 is required to have a low resistance in order to avoid display failures such as non-uniformity, crosstalk or the like caused by signal delay of the common electrode. For this purpose, the common wiring 101 is required to have a sufficient width. As a result, in the conventional active matrix substrate as shown in FIG. 18, it is required to maintain not only a region for leading the signal lines S but a region for leading the common wiring 101 of a sufficient width around the pixel region 96, and thus the area of the frame region cannot be reduced.